title: A point mutation in the amino terminus of TLR7 abolishes signaling without affecting ligand binding.
abstract: TLR7 is the mammalian receptor for ssRNA and some nucleotide-like small molecules. We have generated a mouse by N-nitrose-N'-ethyl urea mutagenesis in which threonine 68 of TLR7 was substituted with isoleucine. Cells bearing this mutant TLR7 lost the sensitivity to the small-molecule TLR7 agonist resiquimod, hence the name TLR7(rsq1). In this work, we report the characterization of this mutant protein. Similar to the wild-type counterpart, TLR7(rsq1) localizes to the endoplasmic reticulum and is expressed at normal levels in both primary cells and reconstituted 293T cells. In addition to small-molecule TLR7 agonists, TLR7(rsq1) fails to be activated by ssRNA. Whole-transcriptome analysis demonstrates that TLR7 is the exclusive and indispensable receptor for both classes of ligands, consistent with the fact that both ligands induce highly similar transcriptional signatures in TLR7(wt/wt) splenocytes. Thus, TLR7(rsq1) is a bona fide phenocopy of the TLR7 null mouse. Because TLR7(rsq1) binds to ssRNA, our studies imply that the N-terminal portion of TLR7 triggers a yet to be identified event on TLR7. TLR7(rsq1) mice might represent a valuable tool to help elucidate novel aspects of TLR7 biology.
authors.affiliation: Immunology US, Novartis Vaccines and Diagnostics, Cambridge, MA 02139, USA.
authors.forename: Carlo
authors.initials: C
authors.lastname: Iavarone
authors.forename: Katrin
authors.initials: K
authors.lastname: Ramsauer
authors.forename: Andriy V
authors.initials: AV
authors.lastname: Kubarenko
authors.forename: Jason C
authors.initials: JC
authors.lastname: Debasitis
authors.forename: Igor
authors.initials: I
authors.lastname: Leykin
authors.forename: Alexander N R
authors.initials: AN
authors.lastname: Weber
authors.forename: Owen M
authors.initials: OM
authors.lastname: Siggs
authors.forename: Bruce
authors.initials: B
authors.lastname: Beutler
authors.forename: Pu
authors.initials: P
authors.lastname: Zhang
authors.forename: Gillis
authors.initials: G
authors.lastname: Otten
authors.forename: Ugo
authors.initials: U
authors.lastname: D'Oro
authors.forename: Nicholas M
authors.initials: NM
authors.lastname: Valiante
authors.forename: M Lamine
authors.initials: ML
authors.lastname: Mbow
authors.forename: Alberto
authors.initials: A
authors.lastname: Visintin
mesh_terms: D000818:Animals; D002460:Cell Line; D002478:Cells, Cultured; D057809:HEK293 Cells; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D008024:Ligands; D008562:Membrane Glycoproteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D016297:Mutagenesis, Site-Directed; D017354:Point Mutation / Q000276:immunology*; D011485:Protein Binding / Q000187:drug effects / Q000235:genetics / Q000276:immunology; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics* / Q000276:immunology*; D051199:Toll-Like Receptor 7 / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism*
chemical_list: D007093:Imidazoles; D008024:Ligands; D008562:Membrane Glycoproteins; C495348:TLR7 protein, human; C477038:Tlr7 protein, mouse; D051199:Toll-Like Receptor 7; C402365:resiquimod